To evaluate the safety and to determine the efficacy of D-ribose for the amelioration of fatigue in subjects with fibromyalgia. This is a phase IIa, randomized, double-blind, placebo-controlled, multi-center, multiple dose study of D-ribose versus placebo administered at doses of 5 g three times a day (TID) over a 12-week period to subjects who are experiencing fatigue associated with a diagnosis of fibromyalgia.